1. Field of the Invention
The present invention relates to a pixel structure of an organic light emitting diode display and a manufacturing method thereof, and more particularly, to a pixel structure of an organic light emitting diode display having two diodes with different current-voltage characteristics.
2. Description of the Prior Art
Recently, organic light emitting diode (OLED) displays have become popular flat displays because of having the advantages of self-luminescence, wide viewing angle, fast response time, high illumination efficiency, low operating voltage, thin panel thickness, flexibility and a simple fabricating process, and thus, the OLED displays have been widely applied to various kinds of flat display products.
A pixel structure of the OLED display includes an OLED, a driving transistor and a switching transistor. The driving transistor is electrically connected to the organic OLED so as to control a switch of the OLED. The switching transistor is electrically connected to the driving transistor so as to control a switch of the driving transistor. Generally, in a manufacturing process of the OLED display, the driving transistor and the switching transistor are fabricated by the same process, so that the driving transistor and the switching transistor can have the same current-voltage characteristics. Thus, the driving transistor and the switching transistor have the same subthreshold slope (SS).
However, when the driving transistor and the switching transistor have the same SS, the switching transistor cannot turn on the driving transistor rapidly, so that the OLED display easily generates residual images. Or, the driving transistor provides current having no linear relation with voltage to the OLED, so that the OLED cannot display various brightness variations in relation to different gray levels. For these reasons, to manufacturing the switching transistor and the driving transistor with different current-voltage characteristics is an objective in the industry.